Introduction to Vector Graphics
for Science-n-Stuff

What are vector graphics and why should I care?

Pixelated (bitmap) images are fantastic at conveying photorealism, but they are not always the best choice for displaying detailed and consistent graphical information:

• We cannot scale bitmap images without losing precision:
  Bitmap images are made up of a fixed number of pixels, so they only look their best at a specific size and resolution and become pixelated/blurry when resized (they can be made smaller, but not bigger).

• Bitmaps are often large and resource-hungry:
  Every pixel in a bitmap image is associated with a separate piece of memory in the computer. This means that detailed images can be very large, difficult to edit and share, and their quality is dependent on the software and hardware used to view them.

So what’s so special about vectors?

• Vectors are infinitely scalable with no loss of quality
  Instead of containing a fixed number of square pixels, vector graphics store information about objects as points on a plane, connected by mathematical equations that describe their shape and relationships to one another.

• Files are much smaller
  Vector graphics can be more easily edited, shared and stored than bitmap images.

• The image always looks the same, on screen or printed, regardless of the size or resolution All this makes them a great choice for precise/detailed plots, schematics, infographics, graphical abstracts and posters.

Bitmap image of a zebra finch

Bitmap image of a zebra finch

scaled bitmap image of a zebra finch

Vector drawing of a zebra finch

Vector drawing of a zebra finch

scaled vector drawing of a zebra finch

What’s the catch?

It requires a little bit of practice to get to grips with vector graphics software, but you don’t need to be an artist or designer to make use of these tools. There are some considerations to keep in mind when using vector graphics:

File types

• Most commonly you’ll see .svg (Scalable Vector Graphics). (Svg’s are XML based which makes them easy to render in most web browsers for quick viewing!)
• PDFs can also be vector-based (but not always). Think about how when you zoom into a pdf file the text always remains crisp and clear!
• Another common file type is .eps (Encapsulated PostScript). .EPS in my experience is a favourite of journals because it’s so easily editable and compatible with most design software.
  

Tip! If you’re working in Illustrator, files will be .ai natively, and if you’re working in Inkscape it will be .svg. I recommend you always keep a copy of your file in the native format of the software it was created in, and save any exports as a new version, just incase something goes wrong down the line. It’s easy to export a .ai file into a .eps, but not necessarily the other way around…

Reproducibility

You can easily save plots from R as vectors that can then be edited in a vector graphics software. In RStudio you can use ggsave, in vscode you can save plots directly as svg files from the viewing pane.

It’s important to bear in mind though, that the more heavily manually edited a plot is, the less reproducible it is. Before editing a plot it’s worth asking yourself whether a coding solution might be a better option first!

Colour models

The two main types of colour models are RGB (Red, Green, Blue) (used primarily for digital display) and CMYK (Cyan, Magenta, Yellow, Black) (used primarily for print). It’s important to consider the colours of your work before you start. Just remember that a graphic produced with RGB colours will look different when printed and visa versa.

RGB and CMYK colour modes

Which to choose for both print and screen? There isn’t an obvious answer but I usually create the image in RGB first because of the wider choice of colours available for digital displays. Just remember that before printing, you might want to convert the image to CMYK to ensure accurate colour reproduction.

Note! While Illustrator has a built in engine for converting between colour models, in Inkscape it’s a bit more tricky, and you might have to use a different software - I think Scribus is the most commonly used free option.

Which software should I use?

There are countless options! I’ve dabbled in a few but the two most popular are probably Inkscape and Illustrator. They both have their pros and cons and I’ve listed a few below:

Inkscape	Illustrator
Very accessible (free and open source) with community driven updates	Requires a licences subscription with Adobe (free for UoS staff and students upon request, but expensive otherwise)
.svg native format. May struggle with some complex file types	.ai native format, more flexible at handling complex file types. Seamless workflow with other Adobe software
RGB native colour model, external software needed for colour model conversion	RGB or CMYK colour models easily specified with a built in colour model conversion engine
Can have stability issues, but has fewer system requirements	Pretty stable, however can require a huge amount of RAM for big files and won’t run well on old/certain systems
Lacks some tools and features, however realistically it has everything you need for simple graphics and posters	Has a lot of specialised tools and functions. The industry standard
Many community resources out there for learning, with a shallower learning curve than Illlustrator	Steeper learning curve, so not as suitable for beginners, fewer community resources

I’m going to introduce you to Inkscape today, because I believe it’s the better choice for beginners and it likely has everything you need to produce beautiful plots, posters, scientific drawings and schematics.

So what kind of things can I create with a vector graphics software?

The Inkscape interface